Aircraft tire

ABSTRACT

A pneumatic tire having a carcass and a belt reinforcing structure wherein the belt reinforcing structure is a composite belt structure having at least one radially inner spiral layer and at least one zigzag belt reinforcing structure located radially outward of said spiral layer. The zigzag belt width is preferably wider than the spiral layer.

FIELD OF THE INVENTION

This invention relates to pneumatic tires having a carcass and a beltreinforcing structure, more particularly to high speed heavy load tiressuch as those used on aircraft.

BACKGROUND OF THE INVENTION

Pneumatic tires for high speed applications experience a high degree offlexure in the crown area of the tire as the tire enters and leaves thearea of the footprint. This problem is particularly exacerbated onaircraft tires wherein the tires can reach speed of over 200 mph attakeoff and landing.

When a tire spins at very high speeds the crown area tends to grow indimension due to the high angular accelerations and velocity, tending topull the tread area radially outwardly. Counteracting these forces isthe load of the vehicle which is only supported in the small area of thetire known as the footprint area.

Current tire design drivers are an aircraft tire capable of high speed,high load and with reduced weight. It is known in the prior art to usezigzag belt layers in aircraft tires, such as disclosed in the WatanabeU.S. Pat. No. 5,427,167. Zigzag belt layers have the advantage ofeliminating cut belt edges at the outer lateral edge of the beltpackage. The inherent flexibility of the zigzag belt layers also helpimprove cornering forces. However, a tire designed with zigzag beltlayers cannot carry as heavy a load as required by current commercialaircraft design requirements. Further, there is generally a tradeoffbetween load capacity and weight. Thus an improved aircraft tire isneeded, which is capable of meeting high speed, high load and withreduced weight.

DEFINITIONS

“Carcass” means the tire structure apart from the belt structure, tread,undertread, and sidewall rubber over the plies, but including the beads.

“Circumferential” means lines or directions extending along theperimeter of the surface of the annular tread perpendicular to the axialdirection.

“Cord” means one of the reinforcement strands of which the plies in thetire are comprised.

“Equatorial plane (EP)” means the plane perpendicular to the tire's axisof rotation and passing through the center of its tread.

“Ply” means a continuous layer of rubber-coated parallel cords.

“Radial” and “radially” mean directions radially toward or away from theaxis of rotation of the tire.

“Radial-ply tire” means a belted or circumferentially-restrictedpneumatic tire in which the ply cords which extend from bead to bead arelaid at cord angles between 65° and 90° with respect to the equatorialplane of the tire.

“Zigzag belt reinforcing structure” means at least two layers of cordsor a ribbon of parallel cords having 1 to 20 cords in each ribbon andlaid up in an alternating pattern extending at an angle between 5° and30° between lateral edges of the belt layers.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic cross-sectional view of a first embodiment of halfof a tire according to the invention;

FIG. 2 is a schematic perspective view of a zigzag belt layer in themiddle of the formation;

FIG. 3 is a schematically enlarged cross-sectional view of a firstembodiment of half of a composite belt package for a tire showing thebelt layer configuration;

FIG. 4 is a schematically enlarged cross-sectional view of a secondembodiment of a composite belt package showing the belt layerconfiguration;

FIG. 5 is a schematically enlarged cross-sectional view of a thirdembodiment of a composite belt package showing the belt layerconfiguration;

FIG. 6 is a schematically enlarged cross-sectional view of a fourthembodiment of a composite belt package showing the belt layerconfiguration;

FIG. 7 is a schematically enlarged cross-sectional view of a fifthembodiment of a composite belt package showing the belt layerconfiguration;

FIG. 8 is a schematically enlarged cross-sectional view of a sixthembodiment of a composite belt package showing the belt layerconfiguration;

FIG. 9 is a schematically enlarged cross-sectional view of a seventhembodiment of a composite belt package showing the belt layerconfiguration; and

FIG. 10 is a schematically enlarged cross-sectional view of an eighthembodiment of a composite belt package showing the belt layerconfiguration.

FIG. 11 is an enlarged cross-sectional view of a ninth embodiment of abelt package.

FIG. 12 is a close up view of a section of the belt package of FIG. 11.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 illustrates a cross-sectional view of one half of a radialaircraft tire 10 of the present invention. The tire is symmetrical aboutthe mid-circumferential plane so that only one half is illustrated. Asshown, the aircraft tire comprises a pair of bead portions 12 eachcontaining a bead core 14 embedded therein. One example of a bead coresuitable for use in an aircraft tire is shown in U.S. Pat. No.6,571,847. The bead core 14 preferably has an aluminum, aluminum alloyor other light weight alloy in the center portion 13 surrounded by aplurality of steel sheath wires 15. A person skilled in the art mayappreciate that other bead cores may also be utilized.

The aircraft tire further comprises a sidewall portion 16 extendingsubstantially outward from each of the bead portions 12 in the radialdirection of the tire, and a tread portion 20 extending between theradially outer ends of the sidewall portions 16. Furthermore, the tire10 is reinforced with a carcass 22 toroidally extending from one of thebead portions 12 to the other bead portion 12. The carcass 22 iscomprised of inner carcass plies 24 and outer carcass plies 26,preferably oriented in the radial direction. Among these carcass plies,typically four inner plies 24 are wound around the bead core 14 frominside of the tire toward outside thereof to form turnup portions, whiletypically two outer plies 26 are extended downward to the bead core 14along the outside of the turnup portion of the inner carcass ply 24.Each of these carcass plies 24, 26 may comprise any suitable cord,typically nylon cords such as nylon-6,6 cords extending substantiallyperpendicular to an equatorial plane EP of the tire (i.e., extending inthe radial direction of the tire). Preferably the nylon cords have an1890 denier/2/2 or 1890 denier/3 construction. One or more of thecarcass plies 24, 26 may also comprise an aramid and nylon cordstructure, for example, a hybrid cord, a high energy cord or a mergedcord. Examples of suitable cords are described in U.S. Pat. No.4,893,665, U.S. Pat. No. 4,155,394 or U.S. Pat. No. 6,799,618.

The aircraft tire 10 further comprises a belt package 40 arrangedbetween the carcass 22 and the tread rubber 20. FIG. 3 illustrates afirst embodiment of one half of a belt package 40 suitable for use inthe aircraft tire. The belt package 40 is symmetrical about themid-circumferential plane so that only one half of the belt package isillustrated. The belt package 40 as shown comprises a first belt layer50 located adjacent the carcass. The first belt layer 50 is preferablyformed of cords having an angle of 5 degrees or less with respect to themid-circumferential plane. Preferably, the first belt layer 50 is formedof a rubberized strip 43 of two or more cords made by spirally orhelically winding the cords at an angle of plus or minus 5 degrees orless relative to the circumferential direction. The first belt layer 50is the narrowest belt structure of the belt package 40, and has a widthin the range of about 13% to about 100% of the rim width (width betweenflanges), and more particularly in the range of about 20% to about 70%of the rim width (width between flanges), and most particularly in therange of about 30% to about 42% of the rim width (width betweenflanges).

The belt package 40 further comprises a second belt layer 60 locatedradially outward of the first belt layer 50. The second belt layer 60 ispreferably formed of cords having an angle of 5 degrees or less withrespect to the mid-circumferential plane. Preferably, the second beltlayer 60 is formed of a rubberized strip 43 of two or more cords made byspirally or helically winding the cords at an angle of plus or minus 5degrees or less relative to the circumferential direction. The secondbelt layer has a width in the range of about 101% to about 120% of therim width, and has a width greater than the first belt layer 50.

The belt package 40 further comprises at least one zigzag beltreinforcing structure 70. The zigzag belt reinforcing structure 70 iscomprised of two layers of cord interwoven together formed as shown inFIG. 2. The zigzag belt structure is formed from a rubberized strip 43of one or more cords 46, that is wound generally in the circumferentialdirection while being inclined to extend between alternating lateraledges 44 and 45 of a tire building drum 49 or core. The strip is woundalong such zigzag path many times while the strip 43 is shifted adesired amount in the circumferential direction so as not to form a gapbetween the adjoining strips 43. As a result, the cords extend in thecircumferential direction while changing the bending direction at aturnaround point at both ends 44, 45. The cords of the zigzag beltstructure cross with each other, typically at a cord angle A of 5degrees to 30 degrees with respect to the equatorial plane EP of thetire when the strip 43 is reciprocated at least once between both sideends 44 and 45 of the ply within every 360 degrees of the circumferenceas mentioned above. The two layers of cords formed in each zigzag beltstructure are embedded and inseparable in the belt layer and whereinthere are no cut ends at the outer lateral ends of the belt.

It is preferred that the zigzag belt structure 70 is the most radiallyoutward belt structure of the belt package 40. It is additionallypreferred that there is only one zigzag belt structure. The zigzag beltstructure 70 is preferably wider than the first belt structure, and morepreferably is wider than both the first belt structure and the secondbelt structure 60. The ratio of the zigzag belt width Wz to the secondbelt structure 60 width Ws is preferably as follows:

0.6<Ws/Wz<1  (1)

FIG. 6 illustrates an additional embodiment wherein the belt structurefurther includes a second zigzag belt structure 92 located radiallyoutward of the first zigzag belt structure 70. The second zigzag beltstructure 92 has a width less than the first zigzag belt structure 70.The zigzag belt structure 70 is the widest belt, and has a width greaterthan the width of the belt layer 60. This embodiment further includes 4low angle belts, 60, 50, 55, 57 wherein the narrowest belt 55 is locatedradially inward of all the belts, the next widest belt 57 is locatedradially outward of belt 55, the next widest belt 50 is located radiallyoutward of belt 57, and then the widest belt 60.

FIG. 8 illustrates yet another embodiment of the invention. The beltpackage 40 includes two radially outer zigzag belts 92, 70 wherein thezigzag belt 70 is the widest belt of all. The embodiment furtherincludes four low angle belts 52, 54, 56, 58. Two of the low angle belts56, 58 have the widest width of the low angle belts. The radiallyoutward belt 58 is slightly wider than belt 56. There are also tworadially inner low angle belts 52, 54 which have a width of about 25-20%of the width of the belts 56, 58.

FIG. 9 illustrates still another embodiment of the present invention.The embodiment of FIG. 9 includes two radially inner low angle belts 50,60. The belt package further includes two additional zigzag beltstructures 68, 69 wherein both belt structures are located radiallyoutward of the first zigzag belt structure 70. The belt structures 68,69, 70 have decreasing belt widths so that the radially innermost beltis the widest belt, and the radially outermost belt 68 is the narrowest.FIG. 10 illustrates a variation of the embodiment of FIG. 9 wherein athird low angle belt 51 is located radially inward of low angle belt 50and has a width in the range of about 13% to about 47% of the rim widthbetween the flanges.

FIG. 11 illustrates yet another embodiment of the invention. Thisembodiment includes a first and second belt 100, 105 having of low angleof 5 degrees or less with respect to the circumferential plane. Thefirst and second belts 100, 105 are preferably helically wound. Thefirst belt 100 is the radially innermost belt, and has a width Bw_(s).The first belt 100 is the narrowest belt of all the belts. The secondbelt 105 is located radially outward of the first belt, and has aslightly larger width than the first belt. The embodiment furtherincludes a third 110 and fourth belt 115, having a low angle of 5degrees or less with respect to the circumferential plane. The third andfourth belts are preferably helically wound. The third belt 110 islocated radially outward of the second belt, and is substantially widerthan the first and second belts. The third belt has a width bw3. Thefourth belt 115 is located radially outward of the third belt, and isthe widest of the low angle belts. The fourth belt has a width slightlylarger than the third belt. The embodiment further includes a first 120and second 130 zigzag belt structure that are both located radiallyoutward of the first through fourth belts. The first zigzag belt 120 islocated radially outward of the fourth belt 115, and has the widestwidth BwZ of all of the belts. The ratio of the zigzag belt width BWz tothe narrowest cut belt Bws is as follows:

0.3<BWs/BWz<0.6, and more preferably in the range of0.3<BWs/BWz<0.5  (1)

In the above embodiment, it is additionally preferred that the ply bemade of nylon and that the belt be made of an aramid/nylon blend, suchthat the ply cord % elongation is greater than the belt cord %elongation at break. It is additionally preferred that the maximum beltcord elongation at break be less than 18%.

Near the axially outer ends 122 of the first zigzag belt, a first cutstrip 140 is placed between the first zigzag belt end and the fourthbelt. A second cut strip 150 is placed between the first and secondzigzag belt structures 120, 130. The first cut strip 140 extends axiallyinward from the axially outer edge of the first zigzag belt a definedwidth W2. The second strip extends axially inward from the axially outeredge of the second zigzag belt a defined width W1. The defined width W1and W2 is in the range of 1% to 12% of the width of the widest zigzagbelt 120. The thickness of each strip Et is in the range of:

0.5Cd≦Et<3Cd,

wherein Cd is the diameter of the cord of the zigzag belt structure.

The thickness of the strip Et is preferably in the range of:

0.5Cd≦Et<2Cd

The thickness of the strip Et is more preferably in the range of:

Cd≦Et<2Cd

FIG. 12 is a close up view of FIG. 11, illustrating the placement of thefirst and second strips between the fourth belt and the first zigzagbelt, and between the first and second zigzag belts.

TABLE 1 Ex. 1 2 3 4 5 6 7 Ply Nylon Nylon Nylon Nylon Nylon Nylon Nylon1890d/3 1890d/2/2 1890d/3 1890d/3 1890d/3 1890d/3 1890d/3 Belt NylonNylon Nylon Aramid Aramid/Nylon Aramid/Nylon Aramid/Nylon 1890d/31890d/2/2 1890d/2/2 3000d/3 3000d/2 + 1680d/2 3000d/2 + 1680d/33000d/2 + 1680d/4 Ply cord 22 23 22 22 22 22 22 Elong. % Belt cord 25 2325 25 14 14 14 % elong. BWs/BWZ .63 .63 .63 .63 .41 .41 .41 Et/Cd 0.250.26 0.26 0.30 0.30 1.10 1.25 Belt ends 22 20 20 18 18 18 18 per inTread cut Blew Blew Blew Pass Pass Pass Pass test Tire 100 103 105 98 99160 160 durability index Weight 100 97 98 86 86 86 87 index

The first cut strip 140 may also be placed between belts 60 and 70 ofFIGS. 3 through 10 in the manner as described above. The second cutstrip may also be placed between belts 70 and 90 of FIG. 5, and belts 70and 92 of FIGS. 6-8, and between belts 69 and 70 of FIGS. 9 and 10.

In the table I above, a series of tires having size 46x17.0R20 30PR weremade. The tires were tested at the following conditions: Rated load:46000 lbs, Rated pressure: 222 psi, 40 mph speed. Durability testcondition: FAA TSO C62e. Tread cut test condition: dropping metal bladebetween tire and drum during rotating tire under rated condition.

Three tires labeled as 1-3, were made from nylon ply and nylon belts.All three tires had a BWs/BWz of 0.63 and a Et/Cd ratio in the range of0.25-0.26. All three examples failed the tread cut test, although tiredurability index ranged from 100 to 105. The weight index ranged from100 to 97. Tire example 4 had the same characteristics as the otherthree examples, except that the belt was made of aramid, and the Et/Cdratio was increased to 0.3. The tire passed the tread cut, but thedurability index decreased to 98. The weight index was significantlydecreased to 86. In example 5, the belt was made of an aramid/nyloncord, the belt width ratio BWs/BWz was significantly decreased to 0.41and the Et/Cd ratio was 0.3. The tire passed the tread cut test and tiredurability slightly improved. In example 6, the Et/Cd ratio wassignificantly increased to 1.1 and the tire durability significantlyincreased to 160 from 99 of example 5. Examples 5 and 6 are essentiallythe same except for the Et/cd ratio. Example 7 is similar to 6, exceptthe Et/Cd ratio was increased to 1.25, which resulted in samedurability.

In any of the above described embodiments, the cords are preferablycontinuously wound from one belt structure to the next.

The cords of any of the above described carcass, spiral or zigzag beltlayers described above may be nylon, nylon 6, 6, aramid, or combinationsthereof, including merged, hybrid, high energy constructions known tothose skilled in the art. One example of a suitable cord constructionfor the belt cords, carcass cords (or both), may comprise a composite ofaramid and nylon, containing two cords of a polyamide (aramid) withconstruction of 3300 dtex with a 6.7 twist, and one nylon or nylon 6/6cord having a construction of 1880 dtex, with a 4.5 twist. The overallmerged cable twist is 6.7. The composite cords may have an elongation atbreak greater than 11% and a tensile strength greater than 900 newtons.Optionally, the original linear density may be greater than 8500 dtex.Elongation, break, linear density and tensile strength are determinedfrom cord samples taken after being dipped but prior to vulcanization ofthe tire.

Variations of the present invention are possible in light of thedescription as provided herein. While certain representative embodimentsand details have been shown for the purpose of illustrating the subjectinventions, it will be apparent to those skilled in the art that variouschanges and modifications can be made without departing from the scopeof the subject inventions.

What is claimed is:
 1. A pneumatic tire having a carcass and a beltreinforcing structure, the belt reinforcing structure comprising: Afirst belt layer having cords arranged at an angle of 5 degrees or lesswith respect to the midcircumferential plane, and a zigzag beltreinforcing structure, the zigzag belt reinforcing structure forming twolayers of cords, the cords inclined at 5 to 30 degrees relative to thecenterplane of the tire extending in alternation to turnaround points ateach lateral edge, wherein the zigzag belt reinforcing structure iswider than the first belt layer and is located radially outward of thefirst belt layer, wherein there is a cut belt located between theaxially outer edges of the first belt layer and the zigzag belt layer,wherein the cut belt does not extend under the crown of the tire.
 2. Thepneumatic tire of claim 1 wherein the width of the cut belt layer is inthe range of 1% to 12% of the zigzag belt structure width, as measuredfrom the axially outer position of the zigzag belt structure.
 3. Thepneumatic tire of claim 1 wherein the cut belt layer has a thickness Etgreater than or equal to ½ Cd, wherein Cd is the cord diameter of thezigzag belt structure.
 4. The pneumatic tire of claim 1 wherein the cutbelt layer has a thickness Et less than 3 Cd, wherein Cd is the corddiameter of the zigzag belt structure.
 5. The pneumatic tire of claim 1wherein the cut belt layer has a thickness Et greater than or equal to ¾Cd, wherein Cd is the cord diameter of the zigzag belt structure.
 6. Thepneumatic tire of claim 1 wherein the cut belt layer has a thickness Etless than 2 Cd, wherein Cd is the cord diameter of the zigzag beltstructure.
 7. The pneumatic tire of claim 1 wherein the width of the cutbelt layer is in the range of 3% to 11% of the zigzag belt structurewidth, as measured from the axially outer position of the zigzag beltstructure.
 8. The pneumatic tire of claim 1 wherein the first belt layeror the zigzag belt structure has cords having a percent elongation atbreak less than 18% when measured on a cured tire, and a break strengthgreater than about 900 N when measured on a cured tire.
 9. The pneumatictire of claim 1 wherein the first belt layer or the zigzag beltstructure has cord endings having greater than 15 cords per 1 inchlength.
 10. The pneumatic tire of claim 1 wherein the first belt layeror the zigzag belt structure has cords made of aramid and nylon fibers.11. The pneumatic tire of claim 1 wherein the first belt layer is formedfrom helically winding the cords forming a spiral layer.
 12. Thepneumatic tire of claim 1 wherein the ratio of the zigzag belt width Wzto the widest belt layer width Ws is in the range of about: 0.6<Ws/Wz<1.13. The pneumatic tire of claim 1 wherein one or more of the beltscomprise cords made of a nylon and aramid blend.
 14. The pneumatic tireof claim 1 wherein one or more of the belts comprise cords made ofaramid.
 15. The pneumatic tire of claim 1 further comprising a thirdbelt layer located radially inward of the first and second belt layers,wherein the third belt layer has a width less than the first belt layerand a width less than the second belt layer.
 16. The pneumatic tire ofclaim 1 wherein the belt structure further comprises: two radially innerspiral belt layers, two zigzag belt structures and two radially outerspiral belt layers.
 17. The pneumatic tire of claim 1 wherein at leastone belt ply layer has cords having a percent elongation at breakgreater than about 11%, and a break strength greater than about 900Nwith an original linear density of greater than about 8500 dtex.
 18. Apneumatic tire having a carcass and a belt reinforcing structure, thebelt reinforcing structure comprising: a first belt layer having cordsarranged at an angle of 5 degrees or less with respect to themidcircumferential plane, and a first and second zigzag belt reinforcingstructure, the zigzag belt reinforcing structure forming two layers ofcords, the cords inclined at 5 to 30 degrees relative to the centerplaneof the tire extending in alternation to turnaround points at eachlateral edge, wherein the first and second zigzag belt reinforcingstructure are each located radially outward of the first belt layer,wherein there is a first cut belt located between the axially outeredges of the first belt layer and the zigzag belt layer, wherein thereis a second cut belt located between the axially outer edges of thefirst zigzag belt structure and the second zigzag belt structure,wherein the first cut belt and the second cut belt do not extend underthe crown of the tire.
 19. The pneumatic tire of claim 18 wherein thewidth of the first cut belt layer is in the range of 1% to 12% of thezigzag belt structure width, as measured from the axially outer positionof the zigzag belt structure.
 20. The pneumatic tire of claim 18 whereinthe first cut belt layer has a thickness Et greater than or equal to ½Cd, and has a thickness Et less than 3 Cd, wherein Cd is the corddiameter of the zigzag belt structure.
 21. The pneumatic tire of claim18 wherein the first cut belt layer has a thickness Et greater than orequal to ¾ Cd and less than 2 Cd, wherein Cd is the cord diameter of thezigzag belt structure.
 22. The pneumatic tire of claim 18 wherein thewidth of the first cut belt layer is in the range of 3% to 11% of thezigzag belt structure width, as measured from the axially outer positionof the zigzag belt structure.
 23. The pneumatic tire of claim 18 whereinthe second cut belt layer has a thickness Et greater than or equal to ½Cd, and has a thickness Et less than 3 Cd, wherein Cd is the corddiameter of the zigzag belt structure.
 24. The pneumatic tire of claim18 wherein the second cut belt layer has a thickness Et greater than orequal to ¾ Cd and less than 2 Cd, wherein Cd is the cord diameter of thezigzag belt structure.
 25. The pneumatic tire of claim 18 wherein thewidth of the second cut belt layer is in the range of 3% to 11% of thezigzag belt structure width, as measured from the axially outer positionof the zigzag belt structure.